Technical Abstract:
The objective was to examine parasite infection levels during summer months in growing lambs grazing novel endophyte-infected (NE) or endophyte-infected (EI) tall fescue and examine third stage larval development from feces collected from lambs or calves grazing NE, endophyte-free (EF) or EI tall fescue. Lambs grazed NE or EI tall fescue plots (n = 4 lambs for each of six 0.4 ha plots/forage type) and were inoculated with 5,000 L3 larvae (97% H. contortus). Individuals were dewormed when PCV declined below 20. In mid-July individual fecal samples were collected for coproculture. After 14 d, larvae were counted, identified per 100 ml and percentage of eggs hatched and number of larvae/g feces determined. PCV was greater for lambs grazing NE in May and July than those grazing EI fescue, but less in June and similar between treatments in August (forage × date, P < 0.004). FEC increased between April and August for both groups of lambs and was greater in early August in NE lambs (forage × date, P < 0.05). There tended to be a greater number of larvae hatched from lambs grazing EI compared with those grazing NE forage (2108 > 1284 L3/g; P < 0.08) and greater percentage hatched from lambs grazing EI (50.9 ± 12.1 > 24.0 ± 9.3%;P < 0.09). Differences in FEC between lambs grazing NE or EI tall fescue was likely due to differences in forage height. Percentage of H. contortus (83.4%), Trichostrongylus sp. (16.2%), and Oesophagostumum sp. (0.4%) were similar between forage treatments. In a second study, calves with dams frazed EF (n = 20) or EI (n = 28) tall fescue since birth. In late July FEC and PVC were determined and fecal samples from 10 calves from each forage were cultured. In calves, FEC (303 eggs/g) and PCV (35%) were similar between fescue varieties. Number of L3 larvae cultured tended to be greater in EI calves (121.7 > 55.2 L3/g; P < 0.08), but percentage L3 hatched from eggs was similar between forage groups. Percentage of Ostertagia sp. and Cooperia sp. were similar between forage groups. Number of cultured L3 larvae from feces collected from lambs and calves may have been reduced in NE or EF compared with EI fescue. Nematode populations cultured from feces were similar between animals grazing NE or EF and EI fescue.